The enzymes are the mediators of the metabolism and the interference of heavy metals with osmoregulatory mechanisms may influence the osmotic pressure, cardiac function and nerve conduction sequentially. The presence of Spirulina platensis might have protected the protein part of the enzyme despite the fish species were exposed to sub-lethal levels of zinc in Labeo rohita, Clarias batrachus & Channa punctatus reflects that the aquatic autotrophs have soothing impact hence the fish species are able to survive under ability of' adaptation for survival. In the present study the influence of Spirulina platensis on sub - lethal concentrations of zinc on phosphofructokinase in cerebrum, diencephalon, cerebellum and medulla oblongata in Labeo rohita (Ham.), Clarias batrachus (Linn.) and Channa punctatus (Bloch) under chronic studies (15,30 & 45 days).
